Is the smell inside the camper or outside only? or both?
If you have 2 tanks, turn one tank off completely and open the other. See if there is still a smell after 15 minutes. If not, turn on the other tank and turn off the first. Wait 15 minutes. Is there a smell? If so, it's tank specific.
Now turn on both tanks? Smell? It's not the tanks then. Start with the regulator and start the soap-em-up treatment.
I had a leaky tank for years. As long as I kept the valve closed, it never leaked, or smelled. But when I turned it on, it would smell sometimes, depending on the way the wind blew. I only run one tank at a time and fill it immediately when it's empty, so I basically ran only the 1 tank and switched over just long enough to get the first one filled. I never did replace that tank. When we sold the camper for our current one, I made sure the dealer new the one tank lost propane. He didn't care and it didn't change any value in the cost of the trade. But running on the one tank only, we never had smell. Turn on the other one, and there was (sometimes) a faint gas smell.
Check your tanks, one at a time. It's an easy way to eliminate if it's the tank or not.